The resize event fires when the document view (window) has been resized.

Bubbles No
Cancelable No
Interface UIEvent
Event handler property onresize

In some earlier browsers it was possible to register resize event handlers on any HTML element. It is still possible to set onresize attributes or use addEventListener() to set a handler on any element. However, resize events are only fired on the window object (i.e. returned by document.defaultView). Only handlers registered on the window object will receive resize events.

There is a proposal to allow all elements to be notified of resize changes. See Resize Observer to read the draft document, and GitHub issues to read the on-going discussions.

Examples

Window size logger

The following example reports the window size each time it is resized. Bear in mind that since the example is running in an <iframe>, you'll need to actually get the <iframe> to resize before you see an effect.

<p>Resize the browser window to fire the <code>resize</code> event.</p>
<p>Window height: <span id="height"></span></p>
<p>Window width: <span id="width"></span></p>
const heightOutput = document.querySelector('#height');
const widthOutput = document.querySelector('#width');

function reportWindowSize() {
  heightOutput.textContent = window.innerHeight;
  widthOutput.textContent = window.innerWidth;
}

window.onresize = reportWindowSize;

addEventListener equivalent

You could set up the event handler using the addEventListener() method:

window.addEventListener('resize', reportWindowSize);

Specifications

Specification Status
Document Object Model (DOM) Level 3 Events Specification
The definition of 'resize' in that specification.
Obsolete
CSS Object Model (CSSOM)
The definition of 'resize' in that specification.
Working Draft

Browser compatibility

No compatibility data found. Please contribute data for "api.Window.defaultView.resize_event" (depth: 1) to the MDN compatibility data repository.

See also